To use postgresql "SELECT FOR UPDATE" in EF Core with linq - FromSqlRaw

Question

Im trying to use the postgresql's ROW LOCK in EF Core. I have a .net core application and postgresql database.

In GetUserContainer function, I build my queries using the FromSqlRaw, as below

var query = db.UserContainers.FromSqlRaw($"SELECT *, xmin FROM tableName {rowlock}")
     .Where(uc => uc.Id == id);

Where rowLock is a function parameter whose value can be "FOR UPDATE" or "FOR SHARE".

I use the below code to read the UserContainers and update

await Task.WhenAll(
   Task.Run(async () =>
   {
    using (var ctx = DbFixture.GetCtx()){
    var repo = new PgUserRepository(ctx);
    var usertoupdate = await repo.GetUserContainer(containerId, 
    dealershipId, eTag, true);
    repo.UpdateUserContainer(usertoupdate, usertoupdate.eTag);
  await repo.Commit();
   }}),
  Task.Run(async () =>
  {
  var message = await TypeOneChannel.Reader.WaitToReadAsync();
  using (var ctx = DbFixture.GetCtx()){
   var repo = new PgUserRepository(ctx);
  repo.Invoking(async (userContainer) => 
  await repo.GetUserContainer(containerId, dealershipId, eTag, true))
  .Should()
 .Throw<Exception>("Because the row is exclusively locked by other task");
 }}));

Note: the snippets of functions used in the above code are as below

 public UserContainer UpdateUserContainer(UserContainer item)
    {
       return db.UserContainers.Update(item).Entity;
    }

 public async Task Commit()
    {
       await db.SaveChangesAsync();
    }

As per the code and the row lock concept, I expect, the getusercontainer in the second task to either fail or wait until the row lock is released, as it is locked by first task.

Im trying to ensure an ACID transaction for updating the user from application side. Postgresql documentation (ROW LOCK) makes it clear that it is possible in SQL, however I need to implement this in C#.

Is there anything I'm doing wrong/missing important details? Or any suggestions to achieve this with a new approach are welcome.